The DP data is commonly misunderstood. Influenza and COVID-19 (probably) both have a strongly age dependent IFR curve. The “COVID-19 is similar to influenza” model predicts IFR in the 1% range for a retiree age distribution like on DP but 0.1% range on the US age distribution. To a first approximation almost all the deaths are in the 65+ age groups, which are a small fraction of US population but about 50% of DP—it was a geriatric cruise.
So the DP is fairly strong evidence for influenza like mortality. I have an analysis here with more details, and this post by Nic Lewis has a more detailed analysis which considers a few more factors.
The “COVID-19 is similar to influenza” model predicts IFR in the 1% range for a retiree age distribution like on DP but 0.1% range on the US age distribution.
FWIW I tried to do an age adjustment for the Diamond Princess myself and what I got was that the 1.4% IFR for the cruise demographics translates into a 0.3% IFR for US demographics (factoring out gender adjustments). I think you could argue that because women were underrepresented on the cruise ship, the adjustment should be greater, so 0.25% is plausible. That said, this doesn’t yet factor in that the people who are medically worst off probably don’t book cruises, so my best-estimate adjustment is maybe 0.4% with a lot of uncertainty. I agree that the people who use the Diamond Princess as evidence for an IFR around 0.9% or higher seem to be making a mistake. At the same time, I do think the Diamond Princess is at least weak to moderate evidence against the 0.125% figure Ioannidis arrived at, or the 0.1% figure that I’ve seen discussed elsewhere.
I don’t really know how this compares to flu mortality, but I found myself somewhat skeptical about the claim I quoted above. You seem to get a 10x update for your age adjustment, whereas my update was only about 5.7x (before factoring in harder-to-quantify assumptions that IMO reduce the factor a bit more even).
(I made a huge mess of my calculations and I don’t recommend clicking on the following link, but just so people see that I’m not just making this up, here’s some evidence that I did something with numbers. Could also be that I neglected some considerations. For factoring in how much overrepresentation of age bracket 70-79 changes things, I based the adjustment off of previous estimates on how strongly Covid19′s IFR is age skewed. I’d imagine that this adjustment was uncontroversial because whether you subscribe to the low IFR theory or not, probably there’s no reason to question whether the proportionalities of the attack rate are correctly reported?)
For a really rough analysis, the overall IFR on the DP was probably about 1% (10 deaths / 1000 infections) after adjusting slightly for false negatives / missed tests.
All those deaths are 70+ age with an in IFR in that group ~2%. About 10% of the US population is in the 70+ bracket, so the projected IFR is ~0.2%. However about half the deaths were in the 80+ age bracket, and if you do a more fine grained binning it’s probably more like 0.15%, but it’s not a high precision estimate.
The DP data is commonly misunderstood. Influenza and COVID-19 (probably) both have a strongly age dependent IFR curve. The “COVID-19 is similar to influenza” model predicts IFR in the 1% range for a retiree age distribution like on DP but 0.1% range on the US age distribution. To a first approximation almost all the deaths are in the 65+ age groups, which are a small fraction of US population but about 50% of DP—it was a geriatric cruise.
So the DP is fairly strong evidence for influenza like mortality. I have an analysis here with more details, and this post by Nic Lewis has a more detailed analysis which considers a few more factors.
FWIW I tried to do an age adjustment for the Diamond Princess myself and what I got was that the 1.4% IFR for the cruise demographics translates into a 0.3% IFR for US demographics (factoring out gender adjustments). I think you could argue that because women were underrepresented on the cruise ship, the adjustment should be greater, so 0.25% is plausible. That said, this doesn’t yet factor in that the people who are medically worst off probably don’t book cruises, so my best-estimate adjustment is maybe 0.4% with a lot of uncertainty. I agree that the people who use the Diamond Princess as evidence for an IFR around 0.9% or higher seem to be making a mistake. At the same time, I do think the Diamond Princess is at least weak to moderate evidence against the 0.125% figure Ioannidis arrived at, or the 0.1% figure that I’ve seen discussed elsewhere.
I don’t really know how this compares to flu mortality, but I found myself somewhat skeptical about the claim I quoted above. You seem to get a 10x update for your age adjustment, whereas my update was only about 5.7x (before factoring in harder-to-quantify assumptions that IMO reduce the factor a bit more even).
(I made a huge mess of my calculations and I don’t recommend clicking on the following link, but just so people see that I’m not just making this up, here’s some evidence that I did something with numbers. Could also be that I neglected some considerations. For factoring in how much overrepresentation of age bracket 70-79 changes things, I based the adjustment off of previous estimates on how strongly Covid19′s IFR is age skewed. I’d imagine that this adjustment was uncontroversial because whether you subscribe to the low IFR theory or not, probably there’s no reason to question whether the proportionalities of the attack rate are correctly reported?)
For a really rough analysis, the overall IFR on the DP was probably about 1% (10 deaths / 1000 infections) after adjusting slightly for false negatives / missed tests.
All those deaths are 70+ age with an in IFR in that group ~2%. About 10% of the US population is in the 70+ bracket, so the projected IFR is ~0.2%. However about half the deaths were in the 80+ age bracket, and if you do a more fine grained binning it’s probably more like 0.15%, but it’s not a high precision estimate.
Very good analysis.
I also thought your recent blog was excellent and think you should make it a top level post:
https://entersingularity.wordpress.com/2020/03/23/covid-19-vs-influenza/